1. Technical Field
The present invention relates to an energy storing apparatus, and more particularly, to a battery pack, a battery apparatus including the same, and a cell balancing method thereof.
2. Related Art
Starting from a hybrid electric vehicle (HEV), an electric vehicle (EV) has developed to a plug-in hybrid electric vehicle (PHEV). Furthermore, the development and management of a battery serving as a power source is one of main concerns of the EV market, and many battery makers are devoting all their strength to preoccupy new techniques.
Recently, much attention has been paid to a smart grid which is an intelligent electric power network system in which a supplier and a consumer interact with each other through information communication technology combined with production, transport, and consumption processes for electricity, thereby increasing efficiency.
The EV or smart grid uses a large-capacity energy storing apparatus, and a battery pack obtained by connecting a plurality of cells, for example, 10 to 1,000 cells is used as a power source. Since a large-capacity battery includes a plurality of cells, an imbalance of state of charge (SOC) may occur between the cells, due to characteristic and temperature differences between the cells. The imbalance of SOC has a bad effect on the entire battery performance. In order to solve such a problem, power needs to be transmitted from a cell having a high SOC and a cell having a low SOC. Such a power transmission method is referred to as active cell balancing.
The cell balancing method which is currently used is based on a wired method. That is, power is transmitted from one cell to another cell through a wire by a switch controlled by a battery controller. In the wired cell balancing method, however, when the number of cells increases to several tens or more, the connection between the wire and the switch becomes very complex. Furthermore, since a large number of manual operations are required during a manufacturing process, the manufacturing cost increases.
Therefore, more advanced technology is urgently required for a cell balancing operation of a large-capacity battery apparatus.